EFFECTS OF MACROPHAGE-COLONY-STIMULATING AND GRANULOCYTE-COLONY-STIMULATING FACTORS OM THYMIDYLATE SYNTHASE AND THYMIDINE KINASE-ACTIVITY IN RAT HEMATOPOIETIC-CELLS

The effects of macrophage (M) and granulocyte (G) colony-stimulating f actors (CSFs) on the activity of thymidylate synthase and thymidine ki nase, which are involved in de novo and salvage pathways for pyrimidin e nucleotide synthesis, were investigated in the hematopoietic cells o f rats treated with cyclophosphamide. Thymidine kinase activity, but n ot that of thymidylate synthase, was markedly enhanced in these cells by M- and G-CSF treatment (p<0.05 and p<0.01). G-CSF directly, and M-C SF indirectly stimulate myeloid cells and lead to S-phase predominantl y via the salvage pathway for pyrimidine nucleotide synthesis. The pre sent study indicates that these CSFs can be effective inducers of comp lete remission in acute leukemias when employed together with chemothe rapy. (C) 1997, Ferrata Storti Foundation.